Colors only process to reduce package yield loss

ABSTRACT

Disclosed is an ordered microelectronic fabrication sequence in which color filters are formed by conformal deposition directly onto a photodetector array of a CCD, CID, or CMOS imaging device to create a concave-up pixel surface, and, overlayed with a high transmittance planarizing film of specified index of refraction and physical properties which optimize light collection to the photodiode without additional conventional microlenses. The optically flat top surface serves to encapsulate and protect the imager from chemical and thermal cleaning treatment damage, minimizes topographical underlayer variations which would aberrate or cause reflection losses of images formed on non-planar surfaces, and, obviates residual particle inclusions induced during dicing and packaging. A CCD imager is formed by photolithographically patterning a planar-array of photodiodes on a semiconductor substrate. The photodiode array is provided with metal photoshields, passivated, and, color filters are formed thereon. A transparent encapsulant is deposited to planarize the color filter layer and completes the solid-state color image-forming device without conventional convex microlenses.

BACKGROUND OF THE INVENTION

[0001] (1) Field of the Invention

[0002] The present invention relates to light collection efficiency andpackage yield improvements for the optical structure and microelectronicfabrication process of semiconductor color imaging devices.

[0003] (2) Description of Prior Art

[0004] Synthetic reconstruction of color images in solid-state analog ordigital video cameras is conventionally performed through a combinationof an array of optical microlens and spectral filter structures andintegrated circuit amplifier automatic gain control operations followinga prescribed sequence of calibrations in an algorithm.

[0005] Typically solid-state color cameras are comprised ofcharge-coupled device (CCD), Charge-Injection Device (CID), orComplementary Metal-Oxide Semiconductor (CMOS) structures with planararrays of microlenses and primary color filters mutually aligned to anarea array of photodiodes patterned onto a semiconductor substrate. Theprincipal challenge in the design of solid-state color camera devices isthe trade-off between adding complexity and steps to the microelectronicfabrication process wherein color filters are integrally formed in thesemiconductor cross-sectional structure versus adding complexity andintegrated electronic circuitry for conversion of the optical analogsignals into digital form and signal processing with color-specificautomated gain-control amplifiers requiring gain-ratio balance. Thetrade-off between microelectronic fabrication process complexity versuselectronic complexity is determined by a plurality of factors, includingproduct manufacturing cost and optoelectronic performance.

[0006] Color-photosensitive integrated circuits require carefullyconfigured color filters to be deposited on the upper layers of asemiconductor device in order to accurately translate a visual imageinto its color components. Conventional configurations may generate acolor pixel by employing four adjacent pixels on an image sensor. Eachof the four pixels is covered by a different color filter selected fromthe group of red, blue and two green pixels, thereby exposing eachmonochromatic pixel to only one of the three basic colors. Simplealgorithms are subsequently applied to merge the inputs from the threemonochromatic pixels to form one full color pixel. The color filterdeposition process and its relationship to the microlens array formationprocess determine the production cycle-time, test-time, yield, andultimate manufacturing cost. It is an object of the present invention toteach color-filter processes which optimize these stated factors withoutthe microlens array(s) and the associated complex process steps.

[0007] While color image formation may be accomplished by recordingappropriately filtered images using three separate arrays, such systemstend to be large and costly. Cameras in which a full color image isgenerated by a single detector array offer significant improvements insize and cost but have inferior spatial resolution. Single-chip colorarrays typically use color filters that are aligned with individualcolumns of photodetector elements to generate a color video signal. In atypical stripe configuration, green filters are used on every othercolumn with the intermediate columns alternatively selected for red orblue recording. To generate a color video signal using an array of thistype, intensity information from the green columns is interpolated toproduce green data at the red and blue locations. This information isthen used to calculate a red-minus-green signal from red-filteredcolumns and a blue-minus-green signal from the blue ones.

[0008] Complete red-minus-green and blue-minus-green images aresubsequently interpolated from this data yielding three complete images.Commercial camcorders use a process similar to this to generate a colorimage but typically utilize more complicated mosaic-filter designs. Theuse of alternate columns to yield color information decreases thespatial resolution in the final image.

[0009] The elementary unit-cell of the imager is defined as a pixel,characterized as an addressable area element with intensity and chromaattributes related to the spectral signal contrast derived from thephoton collection efficiency. Prior art conventionally introduces amicrolens on top of each pixel to focus light rays onto thephotosensitive zone of the pixel.

[0010] The optical performance of semiconductor imaging arrays dependson pixel size and the geometrical optical design of the camera lens,microlenses, color filter combinations, spacers, and photodiode activearea size and shape. The function of the microlens is to efficientlycollect incident light falling within the acceptance cone and refractthis light in an image formation process onto a focal plane at a depthdefined by the planar array of photodiode elements. Significant depth offocus may be required to achieve high resolution images and superiorspectral signal contrast since the typical configuration positions themicrolens array at the top light collecting surface and the photosensorsat the semiconductor substrate surface.

[0011] When a microlens element forms an image of an object passed by avideo camera lens, the amount of radiant energy (light) collected isdirectly proportional to the area of the clear aperture, or entrancepupil, of the microlens. At the image falling on the photodiode activearea, the illumination (energy per unit area) is inversely proportionalto the image area over which the object light is spread. The aperturearea is proportional to the square of the pupil diameter and the imagearea is proportional to the square of the image distance, or focallength. The ratio of the focal length to the clear aperture of themicrolens is known in Optics as the relative aperture or f-number.

[0012] The illumination in the image arriving at the plane of thephotodetectors is inversely proportional to the square of the ratio ofthe focal length to clear aperture. An alternative description uses thedefinition that the numerical aperture (NA) of the lens is thereciprocal of twice the f-number. The concept of depth of focus is thatthere exists an acceptable range of blur (due to defocussing) that willnot adversely affect the performance of the optical system. The depth offocus is dependent on the wavelength of light, and, falls off inverselywith the square of the numerical aperture. Truncation of illuminancepatterns falling outside the microlens aperture results in diffractivespreading and clipping or vignetting, producing undesirablenonuniformities and a dark ring around the image.

[0013] The limiting numerical aperture or f-stop of the imaging camera'soptical system is determined by the smallest aperture element in theconvolution train. Typically, the microlens will be the limitingaperture in video camera systems. Prior Art is characterized by methodsand structures to maximize the microlens aperture by increasing theradius of curvature, employing lens materials with increased refractiveindex, or, using compound lens arrangements to extend the focal planedeeper to match the multilayer span required to image light onto theburied photodiodes at the base surface of the semiconductor substrate.Light falling between photodiode elements or on insensitive outer zonesof the photodiodes, known as dead zones, may cause image smear or noise.With Industry trends to increased miniaturization, smaller photodiodesare associated with decreasing manufacturing cost, and, similarly,mitigate against the extra steps of forming layers for Prior Artcompound lens arrangements to gain increased focal length imaging. Sincethe microlens is aligned and matched in physical size to shrinking pixelsizes, larger microlens sizes are not a practical direction. Higherrefractive index materials for the microlens would increase thereflection-loss at the air-microlens interface and result in decreasedlight collection efficiency and reduced spectral signal contrast orreduced signal-to-noise ratio. Limits to the numerical aperture value ofthe microlens are imposed by the inverse relationship of the depth offocus decreasing as the square of the numerical aperture, a strongquadratic sensitivity on the numerical aperture.

[0014] Typically, a pixel with a microlens requires a narrower incidentlight angle than a pixel that does not use a microlens, imposingadditional optical design implications for the lens of the camera.

[0015] The design challenge for creating superior solid-state colorimagers is, therefore, to optimize spectral collection efficiency tomaximize the fill-factor of the photosensor array elements withoutvignetting (losses from overfilling) and associated photosensorcross-talk, and, with the minimum number of microelectronic fabricationprocess steps. The present invention is clearly distinguished from PriorArt by introducing at least one high transmittance planar film-layer ofspecified optical and physical properties directly over color-filterswithout the use of microlens arrays.

[0016] This distinction will be further demonstrated in the followingsections by describing the specific related optical conditions to besatisfied at the interfaces between the functional layers comprising thesemiconductor color-imaging device when no microlenses are used.

[0017] On colors only products where no microlens layer is formed, thecolor pixel surface is not flat. The curvature of the color filtersurface will cause incident image light to refract and the imageposition and power-density (viz., irradiance distribution) at the sensorsurface will be changed. These factors could have an effect on pixelsensitivity, signal contract and pixel cross-talk. In the colors onlyprocess, the final product wafer suffers significant topographystep-height variations. During the package dicing step, residueparticles remain embedded as a result of the topographical problem. Theresulting entrapped residue particles impact the image quality and causeyield loss of CMOS/CCD image sensor products.

[0018]FIG. 1 exhibits the conventional Prior Art vertical semiconductorcross-sectional profile and optical configuration for color imageformation. Microlens 1 residing on a planarization layer which serves asa spacer 2 collects a bundle of light rays from the image presented tothe video camera and converges the light into focal cone 3 ontophotodiode 8 after passing through color filter 4 residing onplanarization layer 5, passivation layer 6, and metallization layer 7.

[0019] The purpose of the microlens' application in CCD and CMOS imagingdevices is to increase imager sensing efficiency. FIG. 2 illustrates thegeometrical optics for incident image light 9 converged by microlenselement 10, color filter 11, into focal cone 12, to the focal area 13within a photoactive area 14 surrounded by a dead or non-photosensitivearea 15, wherein the sum of the areas of 14 and 15 comprise the regionof the pixel.

[0020] Otsuka in U.S. Pat. No. 6,040,591 teaches a charge-coupled device(CCD) imaging array having a refractive index adjusting and planarizinglayer over a microlens array layer to correct for non-normal angles ofincidence affect on the image light convergence positions at thephotosensor planar array and for interfacial reflection loss at themicrolens surface. Otsuka assumed a typical refractive index value ofn=1.75 for a reflowed polyimide resin microlens and selected afluororesin from Asahi Glass Co., Ltd of refractive index n=1.34 for theindex adjusting layer. That is, Otsuka uses an index of refraction forthe refractive index adjusting layer which is lower than the microlen'sindex to assure bending image light rays inward toward thesurface-normal to obviate vignetting at the sensor active area. FIG. 3shows the CCD cross-sectional structure of the preferred embodiment ofOtsuka's referenced patent, comprised of a photodiode 28, chargetransfer portion 17, formed in a semiconductor substrate 26, having avertical transfer electrode 18, a light shielding film 19 covering thevertical transfer electrode 18, a transparent flattening film 20covering the photodiode 28 and light shield 18, a color filter 21 formedon the flattening film 20, a flattening film 22 formed on the colorfilter 21, a hemispherical microlens 23 formed on the transparentflattening film 22, and a transparent film 24 having refractive indexlower than that of the microlens formed to cover the microlens. A finaloptional top-surface antireflection coating 25 is then formed on thefilm 24. Incident light, L, is shown to converge at the new, deeperfocal point F, instead of the unadjusted shallower value of f0 whichoccurs when the index-adjusting film 24 is absent. It is noted, then,that the indices of refraction and all the prescribed layer thicknessestaught by Otsuka in the referenced patent correspond to optical designsaccommodating the geometric and physical optical characteristics of theformed microlens, not those of the color filter layer(s). No specialtreatment or specified conditions are provided for adjustment of theplanarizing spacer layer 22, nor are interface conditions between thecolor filter layers 21 and planarizing spacer layer 22 addressed. Thecase of no microlens is not considered by Otsuka. Otsuka does considerusing the index-adjusting layer as a transparent sealing resin which canbe hardened and used to seal the solid-state imager as a package. It isnoted that any contaminants captured in the microlens interstices willnot be removed in a final cleaning process step, but will be sealed inas well. Results of embedded particulates will lead to light scatteringnoise effects.

[0021] An alternative approach to microlens optics and devicecross-sectional adaptations, using refractive index structuresconfigured to collect and converge image light onto the photodetectingsurface of the pixel, is given by Furumiya in U.S. Pat. No. 5,844,290.It is noted that color filters, color image formation processes, andwhether there is compatibility of Furiyama's structures with colorfilters are not discussed in Furiyama's referenced patent.

[0022] According to FIG. 4 in U.S. Pat. No. 5,844,290 by Furiyama, apreferred embodiment for the solid-state imager is comprised of a CCDstructure formed of n-type silicon substrate 30, p-well 31,silicon-oxide film 38, in which are patterned n-type buried channellayer 34 above p-type layer 35, a pn junction photodiode of p+ typelayer 33 above n-type layer 32 with p+ device isolation 36, and, deviceopening 42 and reading gate 34. Built up above the pn junction aretransfer electrode 39, silicon oxide film 40, light shield film 41,insulator film 43, and, a first region of planarizing resin 45vertically contiguous with a second region of planarizing resin layer44, forming a top surface plane for microlens array 46.

[0023] The geometrical optics for capturing and converging image lightto the photosensor plane of the CCD is depicted by normal incident lightI gathered in a focal cone of the microlens. The extreme rays arerefracted by the second (vertical) region of planarizing resin layer 44into the first region of planarizing resin layer 45, to a focal point inproximity to the photodiode surface. The first region 45 is in the formof a cylindrical column and is positioned between the n-type layer 32and a center portion of the microlens 46. The second region 44surrounding the first region 45 has a refractive index larger than arefractive index of the first region, assuring the image light bendsinwards toward the surface normal. This coaxial cylindrical arrangementcan, as Furumiya states, be subject to reflection losses at the boundarybetween the planarizing resin layers. It is noted here for the Furumiyareferenced patent, as well as we noted earlier for the Otsuko referencedpatent, that the case of no microlens is not addressed.

[0024] U.S. Pat. No. 5,691,548 to Akio addresses the long focal length,film stack thickness, and vignetting problems common in Prior Art byintroducing a compound lens arrangement comprised of a first positive orconverging convex element in tandem with a negative or diverging(concave upward) second element. The principal problem Akio addresses isfor low light levels the camera's aperture stop must be fully opened.Obliquely incident light rays will noticeably increase in theirproportion to the total amount of all incident image light. Under theseconditions, conventional solid-state imagers will truncate or vignettesignificantly, diminishing their optical sensitivity.

[0025] To solve this problem of conventional imagers not collecting andimaging light efficiently when the aperture is open fully, Akio teachesan optical arrangement so that a concave type microlens layer operatesto collimate light rays collected by the convex lens so as to convergeon the photosensor plane. The color image formation process and the caseof no microlens is not addressed in the referenced Akio patent.

[0026] In U.S. Pat. No. 6,091,093 to Kang et al, an MOS semiconductorimager and microlens process is taught. In particular, embodiments ofthe invention are directed to create a number of gate islandselectrically insulated from each other with spacers. The processesdisclosed aims to integrate logic IC fabrication with photosensors.Conventional processes for polycide-gate or salicide-gate MOS devicesgenerally introduce the problem of inherently forming opaque regionspreventing image light from entering the photosensitive regions of thesilicon at a distance below the surface. Kang et al teach a process forphotocell construction without the conventional additional mask step toprevent the formation of the silicide over those silicon regions thatare patterned for photodetectors. Spacers are formed above thepn-junction of the photodiode array elements such that incident lightpasses through the spacers and into the photosensitive region. As notedpreviously, Kang does not address the color formation process and hisoptical arrangements will not operate without a converging microlens.

[0027] The color filter process and optical film structures taught inthe present invention are clearly distinguished from the Prior Art byeliminating microlenses, and, are shown to include fewer process stepswith improved package final product yield.

[0028] A principal object of the present invention is to teach themethod and structures for adding a specified planarization layer afterthe final color filter layer formation in the colors only product inwhich there are no microlenses. Experiments conducted by the inventorshave demonstrated that the present invention improves pixel sensitivityand reduces the package yield loss through the reduction of residualtrapped particulates induced in the package dicing and cleaning steps.It is an object of the present invention to reduce interfacialreflection losses and vignetting of image light by disclosing a method,structures and optical properties required for refractive indexboundary-engineering.

[0029] Another object of the present invention is to provide an adaptiveprocess wherein antireflection and image-forming structures, spectralcolor filters, and, combinations or varying configurations ofsemiconductor vertical profiles can be integrated with the result ofmaximizing collection efficiency of image intensity patterns on thephotodiode planar arrays to achieve optimum pixel resolution and colorsignal contrast with minimal smear and pixel cross-talk.

[0030] In accord with a principal object of the present invention, thereis provided by the present invention a manufacturing method andmicroelectronic fabrication process sequence which minimizes the numberand task-times of the operational steps required in the production ofsemiconductor arrays for color imaging devices.

[0031] Another object of the present invention is to provide an overcoatprocess allowing the widest and most forgiving process windows for colorfilters and semiconductor integration reproducibility, high reliability,and, consequently maximum process and package yield.

[0032] A further object of the present invention is to obviatetopographical step variations, non-planarity and surface roughnessproblems encountered with conventional Prior Art formation sequences.Prior Art is well known to have step-height or steric effect variationsbetween R/G/B layers and results in departures from designer'sspecifications in transmittance color-balance.

[0033] Avoidance of the specific color pixel lifting problem is a stillfurther object of the present invention.

[0034] To practice the method of the present invention, conventionalmicroelectronic fabrication techniques using photolithographicmaterials, masks and etch tools are employed: in succession the array ofpn-junction photodiodes is patterned with impurity dopants diffused orion-implanted, electrically isolated, and planarized over. In thepresent invention, the colors only process is disclosed wherein colorfilters are geometrically patterned to assemble primary green, red, andblue color filters formed by the addition of suitable dyes or pigmentsappropriate to the desired spectral transmissivity to be associated withspecified photodetector coordinate addresses in the imager matrix andthe algorithm for synthetic color image reconstruction. The microlensprocess steps have been eliminated in the colors only process. A finalspecified planarization layer is applied directly above the color filterlayer to complete the colors only process. The flat top surface isoptimal for the package dicing and final cleaning treatment steps,minimizing particle residues and maximizing product final yield.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The objects, features and advantages of the present invention areunderstood within the context of the Description of the PreferredEmbodiment, as set forth below. The Description of the PreferredEmbodiment is understood within the context of the accompanyingdrawings, which form a material part of this disclosure, wherein:

[0036]FIG. 1 is a simplified schematic cross-sectional profile ofsemiconductor and optical structures showing a typical order of elementsof a conventional Prior Art device for color image formation.

[0037]FIG. 2 illustrates the geometrical optics factors for microlensimaging onto the photosensitive active zone within a square pixel area.

[0038]FIG. 3 depicts the cross-sectional structure and image convergingoptical paths for a Prior Art CCD imager with a single-layer microlens,refractive index adjusting overcoat and top surface antireflection filmlayer.

[0039]FIG. 4 demonstrates a Prior Art cross-sectional structure andimage light collection scheme using vertical coaxial cylindricalsections of higher and lower refractive indices.

[0040]FIG. 5 shows the precedence flow-chart of the process options ofthe present invention.

[0041]FIG. 6A depicts the geometric optics problem of vignettingsuffered by Prior Art processes.

[0042]FIG. 6B shows the general ray trace solution of the new process ofthe present invention to prevent vignetting off the photodetector activearea.

[0043]FIG. 7 is a diagram used to explain an optical path of incidentlight to the photodetector active area, according to the presentinvention.

[0044]FIG. 8A shows the color pixel arrangement along a first principalaxis perpendicular to the plane of the cross-section of thesemiconductor imaging device.

[0045]FIG. 8B shows the color pixel arrangement along a second principalaxis orthogonal to the first principal axis of FIG. 8A and perpendicularto the cross-sectional plane of the semiconductor imaging device.

[0046]FIG. 9 illustrates a possible pixel combination for color imagesynthesis corresponding to the arrangement of color filters shown inFIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] The present invention discloses a significantly simplifiedfabrication sequence and the specific optical conditions and materials'properties to be satisfied in forming a planar film layer of hightransmittance material over at least one layer of color filters toenable high efficiency integrated semiconductor array color imagingdevices without microlenses.

[0048]FIG. 5A and FIG. 5B depicts the simplified comparative fabricationflow-charts of the new process of the present invention whichdistinguish it from the sequence of the Prior Art process. In accordwith the flow-charts shown, the manufacturing method of the presentinvention teaches priority formation of a high transmittance planarizinglayer directly above a color filter layer residing above the sensorelements of the matrix array comprising the semiconductor imager. In thePrior Art process exhibited in FIG. 5A option 1 deposits planarizationlayer 47 prior to color filter formation 48. In FIG. 5A option 2eliminates the planarizing layer and directly deposits the primary colorfilters 48 above the photodiode array. By contrast, FIG. 5B disclosestwo options, both of which teach a final special layer 49; in option 1,special layer 49 is deposited after planarizing layer 47 and colorfilter layer 48 are formed; in option 2, layer 49 follows directdeposition of the color filter layer above the photodiode portion of thepixel.

[0049]FIG. 6A exhibits the image light collection problem suffered inPrior Art processes and structures. In FIG. 6A, incident image light 9from the camera optics is incident normal to the surface of thesolid-state imager, passing from a region of index of refraction N=1(air) into the semiconductor film layers with typical resin refractiveindex of N=1.6. Refraction of the ray bundle results in the outermostrays missing the image plane (vignetting) comprised of the photosensoractive area, and, impinging on the spaces between the photodiodeelements. Light arriving outside the photoelectronic portion of thepixel diminishes sensitivity, signal-to-noise contrast, and induces thephenomenon referred to as “smear” related to the cross-talk effect.

[0050] The new process of the present invention is illustrated in FIG.6B which shows a simple ray-trace for the case of direct deposition ofthe color filters above the photosensor portion of the pixel followed bya specified planarizing layer. In FIG. 6B, normal incident image light 9to the planarizing surface 50 enters from air to a material, such as aresin or polymer, of refractive index N closely matched to that of thecolor filter layer, and, suffers significantly less refraction at theindex interface surface 51, to arrive at the image plane to fill theactive area of the photodiode 14 to a very high order of approximation.A typical case is illustrated for air N=1.0, planarizing layer N=1.5,and for the color filter layer N=1.6.

[0051] An important attribute of the new colors only process of thepresent invention is the conformal concave contour of the interfacesurface 51 shown in FIG. 6B between the color filter layer produced bydirect deposition above the photodiode array 14 of the CCD imager. Thisrefractive index surface contour corresponds to the topology of the CCDsemiconductor device shown in FIG. 8A and FIG. 8B in the region abovethe pn-junction 57. FIG. 7 explains the optical physics of the affect ofincreasing the difference in the index of refraction across the “pixelsurface” 51:

[0052] light ray 9 incident to the “pixel surface” 51 at an angle θ1 tothe surface-normal from a medium of index N1 is refracted at an angle θ2depending on the value of the refractive index N2, according to Snell'sLaw of Refraction:

N1 Sin θ1=N2 Sin θ2  eq.(1)

[0053] If N1>N2, then θ2>θ1.

[0054] For example, if N1=1.0 (air) and N2=1.6 (color filter layer), andif θ1=30 degrees, then θ2=18 degrees. But, if N1=1.5 (specifiedplanarizing layer) and N2=1.6 (color filter layer) and θ1=30 degrees,then θ2′=28 degrees (where ′ denotes ‘prime’).

[0055]FIG. 8A depicts the cross-sectional view of the preferredembodiment of the present invention, showing in particular the priorityformation of the color filter array in mutual registration with thephotoactive regions of the solid-state array imager. FIG. 8A illustratesthe case of a CCD imager fabrication sequence, but it is clearlyrecognized that the present invention equally well applies tocharge-injection device (CID) imagers and CMOS imagers. In FIG. 8A, an“n” (negative) type semiconductor substrate 52, is photolithographicallypatterned by suitable photoresist coating, masking, exposing anddeveloping, to open regions for ion-implant or diffusion doping byselected impurity atoms to form p-(weakly doped positive) type wells 53and 54. With similar photolithography steps, ion-implants or diffusions,an n+ type region 55 is formed to create a pn-junction photodiode and avertical charge coupled device 56. A highly doped positive impurity,p++, is introduced selectively to form a surface isolation layer 57,and, a p-type well 58 is formed to isolate the CCD device 56. To isolatepixels, a p+ channel stop 58 is formed. The gate insulator 59 is thenapplied over the surface of the substrate. The vertical profile iscompleted by processing successive additions of transmission gate 60,interlevel insulator 61, light-shielding layer 62, passivation layer 63,optional planarization layer 64 (cf., FIG. 5B option 1), and in accordwith the preferred embodiment of the present invention, color filters 65for blue (also denoted B) and 66 for green (also denoted G).

[0056]FIG. 8B exhibits the second dimension of the color filter planeformation process, showing the orthogonal direction to that of FIG. 8A.All other semiconductor device structures remain the same for bothfigures. FIG. 8B shows the pixel sequence with the color filter 68 forred (also denoted by R) and the adjacent color filter 65 for blue (B).The color only process is then completed with the deposition of anencapsulant and planarization layer 67, as specified in accord with thepresent invention. Thus, the two-dimensional array of color filtersprovides the color pixel arrangement for synthetic reconstruction ofcamera images without microlenses. FIG. 9 illustrates a possible RBGcolor pixel arrangement, shown inscribed within the dashed-line.

[0057] The processes and structures shown in FIG. 8 will inherentlycreate the pixel surface 51 of FIG. 6 by the conformal nature of theprocess film deposition in forming the color filter layer(s) above thephotodiode regions of the imaging array. The present invention correctsthis inherent concave pixel surface with the index matching planarizinglayer directly deposited after color filter layer formation. Without anindex-matched interface, the concave-up pixel surface will behave as aconcave (negative or diverging) lens element and result in overfillingthe photodiode active area. The features described here are highlyreproducible since they result from precision lithographic patterningand overlays. The resulting structure provides a high degree of finaltop surface flatness which eliminates the topography problems forentrapment of residual particles after package dicing and cleaning.

[0058] The resulting colors only imaging device has, therefore,eliminated the complex and costly steps of Microlens formation whilesustaining high light collection and pixel sensitivity with reducedcross-talk.

[0059] While the invention has been particularly shown and describedwith reference to the preferred embodiments thereof, it will beunderstood by those skilled in the art that various changes in form anddetails may be made without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A microelectronic method of fabricating asolid-state color imaging device in an ordered sequence in which aplanarizing encapsulant layer is adapted for optimizing light collectionthrough integrated color filters to the photodiodes without employmentof conventionl microlenses in a process comprising: a semiconductorsubstrate having a matrix of photodiode elements formed thereon:depositing a passivation coating encapsulating a metal photoshieldlayer, wherein the metal photoshield elements are periodically spaced tocover the areas between the photodiode elements; forming upon thepatterned and encapsulated metal photoshield layer an optional firstoptically transparent planarizing encapsulant layer; forming upon theoptional first optically transparent planarizing encapsulant layer oroptionally directly and conformally on the photodiode passivation andshielding coatings a first patterned color filter layer registered witha subset of the photodiode elements (color pixels); forming upon orintermixed with the first color filter layer a second patterned colorfilter layer in mutual registration with the first color filter layerand a second complementary subset of photodiode elements (color pixels);forming upon or intermixed with the second color filter layer, a thirdpatterned color filter layer in mutual registration with the first andsecond color filter layers and a third complementary subset ofphotodiode elements (color pixels); forming upon the color filterlayer(s) a high transmittance overcoat layer with a planar (flat) topsurface having an index of refraction approximating the index ofrefraction of the color filter layer(s) comprised of red (R), blue (B),green (G).
 2. The method of manufacturing a solid-state color imagingdevice of claim 1, wherein: the semiconductor substrate may be selectedfrom the group consisting of periodic table IV, III-V, II-VI, or othersimple or compound semiconductors.
 3. The method of claim 1, wherein:the photodiode color imaging device may be selected from the groupconsisting of CMOS, CCD, or CID semiconductor devices.
 4. The method ofclaim 1, wherein: a single planarizing encapsulant layer comprises anantireflection coating having thickness equal to an integral multiple ofa quarter-wavelength, such wavelength having a value selected from aspectral average or mean-value.
 5. The method of claim 1, wherein: theplanarizing encapsulant layer is comprised of a negative typephotoresist or a positive type photoresist having refractive index, n,adjusted to match the refractive index of the color filter material. 6.The method of claim 1, wherein: the planarizing encapsulant is comprisedof a patterned multilayer dielectric stack such that one or more color(interference) filters are thereby integrated within the overcoat. 7.The method of claim 1, wherein: the color filter layer or color filterlayers are selected from the group consisting of a patterned dye orpigment loaded material with a tailored concentration profile ofspectral absorbers with tuned absorption coefficients and refractiveindex, a multilayer dielectric or interference stack, photochromics,non-fluorescing or fluorescing dyes, dichroic, or others, with maximumtransmissivity to the photodiode elements.
 8. The method of claim 1,wherein: the planarizing and refractive index matching layer overcoatingthe layer(s) of color filters is comprised of a continuouslygraded-index layer or a discrete stack of stepped index films.
 9. Themethod of claim 1, wherein: the planarizing and refractive indexmatching layer overcoating the layer(s) of color filters is created ormodified by ultraviolet photopolymerization or other radiation, chemicalor thermal means to develop molecular cross-linking to tune the valueand depth profile of the refractive index of said overcoat and/or ofsaid color layer(s).
 10. The structure of claim 1 wherein the colorfilter is comprised of a plane-matrix array comprised of patternedstripes of the same or different colors, ordered clusters of colors orgroupings, multiplanar clusters or groupings, or combinations andpermutations thereof.
 11. A method of manufacturing a solid-stateimaging device according to claim 1, wherein said planarizing andencapsulant layer provides a protective seal against chemical,mechanical or thermal damage induced during dicing, cleaning treatments,or imager device packaging, and provides for reduced final productpackage yield loss and reduced residual particle inclusions within theimaging device.
 12. The structure of claim 1, wherein the color filterlayer has the property of rotary polarization such that light passedthrough such layers will, upon incidence to a lower boundary-layerinterface, be inhibited from retro-transmission and eliminate straylight reflections and image smear.
 13. The structure of the layerscomprising the region over the pn-junction photodiodes and photoshieldsare contoured by photolithographic design and/or microelectronicprocessing, such as reactive ion etching, to produce a specific pixelsurface shape in conjunction with the desired spectral and opticalproperties of the color filter layer(s) and planarizing encapsulantlayer(s) formed thereon, thereby providing a method for controlling thegeometric dimensions, photodiode registration, and concave lens-likeimaging properties of the refractive index boundary comprising the pixelsurface.
 14. The structure of claim 13, wherein an antireflection filmis formed on said planarization and encapsulant layer.
 15. A method ofmanufacturing solid-state imaging devices according to claim 1, whereinthe relative thickness of each color filter layer is regulated to obtainthe desired color gain-balance without changes to any circuit layout.16. The method of claim 1, wherein: the high transmittance overcoat iscomprised of a material satisfying at least the following threerequirements: (1) of index of refraction matched to that of the index ofrefraction of the color filters, e.g., the range n=1.5 to 1.65 (2)thermal resistance>270 degrees Centigrade, (3) transmittance>95%. 17.The method of manufacturing a solid-state imaging device as claimed inclaim 1, wherein the preferred ordered sequence of coating depositionsfor the filter process is blue followed by green followed by red.